A new catalogue of the visible part of the northern part of our home Galaxy, the Milky Way, includes no fewer than 219 million stars.
Geert Barentsen of the University of Hertfordshire led a team who assembled the catalogue in a ten year programme using the Isaac Newton Telescope (INT) on La Palma in the Canary Islands. Their work appears today in the journal Monthly Notices of the Royal Astronomical Society.
From dark sky sites on Earth, the Milky Way appears as a glowing band stretching across the sky. To astronomers, it is the disk of our own galaxy, a system stretching across 100,000 light-years, seen edge-on from our vantage point orbiting the Sun. The disk contains the majority of the stars in the galaxy, including the Sun, and the densest concentrations of dust and gas.
The unaided human eye struggles to distinguish individual objects in this crowded region of the sky, but the 2.5-metre mirror of the INT enabled the scientists to resolve and chart 219 million separate stars. The INT programme charted all the stars brighter than 20th magnitude – or 1 million times fainter than can be seen with the human eye.
Using the catalogue, the scientists have put together an extraordinarily detailed map of the disk of the Galaxy that shows how the density of stars varies, giving them a new and vivid insight into the structure of this vast system of stars, gas and dust.